An electric actuator includes a motor which has a rotor having a motor shaft extending along a central axis and a stator facing the rotor in a radial direction, a motor case for housing the motor, and a deceleration mechanism coupled to one axial side of the motor shaft. The motor case has a case cylinder portion, a lid for covering, and a plurality of screws. The case cylinder portion has a plurality of screw fixing portions. The lid has a top plate portion, an outer cylinder portion which surrounds the case cylinder portion from a radial outer side, an annular groove portion, and a seal member which seals the opening portion of the case cylinder portion. In the lid, an axial thickness of a region which overlaps the annular groove portion as viewed in the axial direction is larger than an axial thickness of the top plate portion.